Investigation of NPFs and CLCs in Nitrate Signaling and Nitrate Distribution among Leaves

• Main Authors: Chan-Yi Lin, 林展伊
• Other Authors: 曲芳華
• Format: Others
• Language: en_US
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/xq5u5k

碩士 === 國立臺灣大學 === 森林環境暨資源學研究所 === 105 === Nitrogen is one of the most important nutrients for plants to grow, and nitrate is the most common form of nitrogen to be absorbed. To utilize nitrate efficiently, higher plants have developed various transporters, including NPFs being responsible for uptake, transport and storage. Of all the 53 genes in NPF, despite some of the members have been well characterized, a lot of them remain unclear. To find if any NPF genes participate in nitrate distribution among leaves, gene expression from public databases, MPSS and e-FP Browser, was analyzed, and nitrate content among leaves of mutants of 19 candidates was measured. The results showed that the nitrate content of young leaf in gtr2-1 was higher than wild type, and more root-fed 15N was transported to young leaf in gtr2-1. The gene expression of GTR2 was higher in young leaf under low nitrate concentration, andβ-glucuronidase reporter analyses indicated that GTR2 were expressed in roots, root-shoot junction, and the young leaves. Taken together, these results suggest that GTR2 might be involved in repressing nitrate allocation to young leaves. In addition, to find out if internal nitrate level would affect primary nitrate response, a nitrate storage defective mutant, clca/clcb, was characterized, and the data showed that CLCa and CLCb might be partly involved in regulating primary nitrate response in roots but not in shoots. This study provides a systematic analysis of the roles of NPFs in nitrate distribution among leaves and found out that GTR2 has a negative impact on nitrate distribution in young leaves. Besides, the study of clca/clcb suggests that external nitrate plays a major role in inducing primary nitrate response.